The present invention relates in general to the field of cogeneration, wherein a gas turbine-generator is used to produce electricity and the turbine exhaust gas is also used as a source of heat and combustion air to produce steam in an interconnected boiler assembly. In particular, the invention relates to the combination of a gas turbine with a factory assembled boiler for steam and/or electric power generation, also referred to as a package boiler, having a low NO.sub.x integrated boiler-burner apparatus which employs a multiple nozzle burner array in its inlet windbox, and other features which improve its operation.
The Babcock & Wilcox Company (B&W), assignee of the present invention and application, designed a conventional boiler which used gas turbine exhaust in the 1950's. The prior art contains several examples teaching the use of turbine exhaust gas in various boiler types. Package boilers, per se, are known from The Babcock & Wilcox Company publication Steam: its generation and use, 40th Edition, at page 25-8. The use of multiple nozzle array burners (also known as duct burners) in the inlet of a heat recovery steam generator (HRSG) to provide an even heat release across the inlet cross-section is also known, and has been used on various turbine exhaust gas boiler applications. See Steam: its generation and use, 40th Edition, page 31-3, and also U.S. Pat. Nos. 4,462,795 and 3,173,523.
A particularly successful package boiler design is known as the FM Package Boiler manufactured by The Babcock & Wilcox Company and disclosed in the publication Steam: its generation and use, 40th Edition, at page 25-8. Other types of package boilers include what are known as "F" type boilers, particularly the PFI (Power for Industry) and PFT (Power for Turbine) types described in Steam: its generation and use, 39th Edition, at pages 25-8 and 25-9. Also known are the "Three Drum Waste Heat Boilers" shown on page 27-10, FIG. 10, of Steam: its generation and use, 39th Edition, and on page 31-8 of Steam: its generation and use, 40th Edition. This latter type of boiler is also known as an "FO" type, and in the industry as simply an "O" type boiler.
The installation of additional water cooled surfaces in the furnace of a boiler to increase heat absorption and reduce furnace temperatures is not new and has been done by the present assignee on many occasions, such as by adding water walls and/or division walls. The application of staged burning with reburning is also not new and has been tried and tested on several B&W boilers and boilers made by others as well. See for example, U.S. Pat. No. 2,653,447. In particular, the use of staging air for NO.sub.x reduction through sidewall ports in package boilers is also known. Additionally, water cooled surface in the form of division walls or wing walls have been supplied on many boilers to increase heat absorption and reduce furnace temperatures.
U.S. Pat. No. 2,298,625 shows the use of a turbine for supplying air around a burner in a heat exchanger. The branching of air from a turbine in U.S. Pat. No. 2,453,938, is used as primary air and as secondary air. U.S. Pat. No. 2,653,447 shows a turbine which supplies combustion air over a first line to an air supply line that is used in conjunction with a coal burner in a boiler having various heat exchange surfaces. The use of recirculated flue gases to reduce NO.sub.x, and even the use of air foils in an inlet burner duct, are disclosed in U.S. Pat. No. 3,781,162. Also see U.S. Pat. No. 4,767,319 for various baffles and control surfaces to help distribute heat in a duct burner arrangement.
The prior art does not contain a teaching that the exhaust of a gas turbine can be utilized in a horizontally fired, factory assembled package boiler having a multi-nozzle burner (MNB) array, and one or more vertically extending, horizontally spaced chill tube assemblies located within a furnace space downstream of the MNB array so as to quickly absorb heat from combustion exhaust gases within the furnace space to lower a temperature of the combustion exhaust gases to minimize NO.sub.x, together with forced draft fan means for providing combustion air and means for supplying fuel to the MNB array; with or without one or more internal duct assemblies positioned in the furnace space for discharging staging gases into the furnace space for NO.sub.x control.